The United right-back
came off with a thigh problem at half-time during his side's 4-1 win over Aston Villa at the weekend and did not train yesterday ahead of the Bayern encounter.

Although Rafael claimed after the game he would be fit for the tie with Bayern, it would be a major risk to start with a player who is struggling with a thigh strain and is not 100 per cent fit.

Informed United sources have suggested David Moyes' back four
will comprise Phil Jones at right-back, experienced duo Nemanja Vidic and Rio Ferdinand in central defence, with Alex Buttner in for the suspended Patrice Evra at left-back.

With Robin van Persie injured with a sprained knee, Wayne Rooney will lead United's attack, with Danny Welbeck and Antonio Valencia expected to provide support in the wide roles.